were found in the tissues vary tenfold in 

 their diameters, and the internal organiza- 

 tion varies from completely syncytial proto- 

 plasm to quite discrete bodies within the 

 parent sphere . Besides this, there are the 

 forms which protrude in a germ tube or 

 hypha from the spheres which are stimulated 

 by means not well "kimwn . In the condition 

 under study here, hyphal forms are found 

 in the tissues of fish very recently killed and 

 fixed shortly after death, as well as in 

 tissues which have been altowed'to age, 

 either within the fish, or in vitro, under re- 

 frigeration. It is impossible to determine 

 which of these many forms are the infective 

 stages, or whether they all are. We have 

 observed that in the viscera of trout which 

 had been held for several days or weeks, or 

 even months, there is a definite progression 

 in the more complete subdivision of proto- 

 plasm of the spheres and within the hyphal 

 stages . There seems to be a high percentage 

 of hyphal stages within the aged tissues. 

 The spheres, which were the prominant 

 stage in the inoculum being fed, could be 

 found unchanged in the intestinal contents of 

 the experimental fish. These experimental 

 fish, which had died of other causes, were 

 examined shortly after feeding. 



Commonly occurring lesions in the wall 

 of the stomach, usually in the distal end, 

 would tend to support the theory that a 

 direct invasion of the host tissue at this 

 site is the normal circumstance when the 

 inoculum is eaten. All parasites seen with- 

 in the host tissue at this site were spherical 

 in shape, and were arranged with several 

 in a cluster as though derived from a cdbx- 

 mon parent or^nism . This would allow 

 for progressive infection through the wall 

 of the stomach and a transperitoneal spread 

 throu^ adjacent viscera, rather than 

 througji being blood-borne. In the intra- 

 peritoneally inoculated fish, found to be 

 positive, the contents of the rectum in- 

 cluded spheres typical for this disease 

 indicating that the reverse migration is 



possible. Transmission of the disease, 

 through water, from chronically chronic- 

 ally infected fish to uniiifeeted fi^h would 

 suggest that stages are able to leave a fish, 

 whether these are spheres or other stages. 



The one experiment on freezing viscera 

 would suggest that this might be a reason- 

 able mechanism for control of Ichthyospor - 

 idium infections in marine fish and other 

 fish viscera which are being fed to hatchery 

 stock . 



SUMMARY 



Transmission experiments demonstrated 

 that Ichthyosporidium sp . , occurring in 

 rainbow trout, can be transmitted by three 

 different methods: through intraperitoneal 

 inoculation of fresh viscera homogenate into 

 susceptible fish; through the feeding of 

 fresh infected viscera; and through indirect 

 contact between living carriers and suscept- 

 ible fish. The host range has been demon- 

 strated to include rainbow trout, Chinook 

 salmon, sockeye salmon, silver salmon, and 

 a cottoid. Fish which were refractory were 

 the goldfish, guppy, squawfish, and catfish. 



LITERATURE CITED 



Ellis^ Marjory F. 



1930 . Ichthyophonus hoferi, a flounder 

 parasite new to North American 

 waters . Proc . and Trans . of the Nova 

 Scotian Institute of Science, 17 (3): 

 185-192. 



Fish, F. F. 



1934. A fungus disease in fishes of the 

 Gulf of Maine . Parasitology, 26 (1): 

 1-16. 



Neresheimer, E., andC. Clodi. 



1914. Ichthyophonus hoferi , der 

 Erreger der Taummelkrankheit der 

 Salmoiden. Arch, fllr Protist, 34 

 (3): 217-248. 



